1. Field of the Invention
The present invention relates to a data reception device capable of correcting an error that has occurred in received data based on check data contained in the received data.
2. Description of the Related Art
Data reception devices for receiving data, including message data, are available in a wide range of sizes from relatively large sizes to relatively small sizes for portable use and attachment to information processing apparatus.
Small-size data reception devices, for example, have been realized as card-type data reception devices for use as unidirectional-communication pagers (so-called "pocket bells") in wide-area communication services and radio modems used as a component of radio LANs (local area networks) for data communication.
FIG. 1 of the accompanying drawings shows an example in which a card-type data reception device 1 is used. The card-type data reception device 1, which is portable, receives data transmitted through a radio channel from a base station when it is carried by the user, and stores message data contained in the received data in an internal memory such as a RAM, for example. For displaying the message data stored in the memory, the card-type data reception device 1 is inserted into a card slot 3 in an information processing apparatus 2 such as a personal computer or the like, and the message data are read from the memory and displayed on a display screen of the information processing apparatus 2.
When the card-type data reception device 1 is inserted as a PCMCIA card in the information processing apparatus 2, the card-type data reception device 1 receives data and stores message data of the received data in the memory, and the stored message is read and displayed on the display screen of the information processing apparatus 2.
In data communications, an error may occur in data while they are being transmitted or received, due to a malfunction of an electric circuit or noise.
Therefore, it has been customary in such data communications for a data transmitter to add an error-correcting code known as a BCH (Bose Chaudhuri Hocquenghem, same is applied hereinafter) code to data to be transmitted, and for a data reception device to detect error bits which are 2 bits or less in the received data and correct them. If an error of more than 2 bits occurs in the received data, then because the error cannot be corrected, the message code in the received data is replaced with a space letter code and stored in the memory.
When the message data stored in the memory which contains such a space letter code are displayed on the display screen of the information processing apparatus, many space letters are contained in the displayed message, making the user uncertain as to whether the displayed space letters are meant to indicate either real space letters or information indicating that the error has not been corrected.
If the card-type data reception device is inserted in the information processing apparatus to process received data, then since the clock signal used in the information processing apparatus for processing data interferes with the received data from the card-type data reception device, the received data from the card-type data reception device are more likely to suffer an error than if the card-type data reception device is carried by the user for receiving data.